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PROLOG | NAME | SYNOPSIS | DESCRIPTION | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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complex.h(0P) POSIX Programmer's Manual complex.h(0P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
complex.h — complex arithmetic
#include <complex.h>
The functionality described on this reference page is aligned with
the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
The <complex.h> header shall define the following macros:
complex Expands to _Complex.
_Complex_I Expands to a constant expression of type const float
_Complex, with the value of the imaginary unit (that
is, a number i such that i2=-1).
imaginary Expands to _Imaginary.
_Imaginary_I
Expands to a constant expression of type const float
_Imaginary with the value of the imaginary unit.
I Expands to either _Imaginary_I or _Complex_I. If
_Imaginary_I is not defined, I expands to _Complex_I.
The macros imaginary and _Imaginary_I shall be defined if and only
if the implementation supports imaginary types.
An application may undefine and then, perhaps, redefine the
complex, imaginary, and I macros.
The following shall be declared as functions and may also be
defined as macros. Function prototypes shall be provided.
double cabs(double complex);
float cabsf(float complex);
long double cabsl(long double complex);
double complex cacos(double complex);
float complex cacosf(float complex);
double complex cacosh(double complex);
float complex cacoshf(float complex);
long double complex cacoshl(long double complex);
long double complex cacosl(long double complex);
double carg(double complex);
float cargf(float complex);
long double cargl(long double complex);
double complex casin(double complex);
float complex casinf(float complex);
double complex casinh(double complex);
float complex casinhf(float complex);
long double complex casinhl(long double complex);
long double complex casinl(long double complex);
double complex catan(double complex);
float complex catanf(float complex);
double complex catanh(double complex);
float complex catanhf(float complex);
long double complex catanhl(long double complex);
long double complex catanl(long double complex);
double complex ccos(double complex);
float complex ccosf(float complex);
double complex ccosh(double complex);
float complex ccoshf(float complex);
long double complex ccoshl(long double complex);
long double complex ccosl(long double complex);
double complex cexp(double complex);
float complex cexpf(float complex);
long double complex cexpl(long double complex);
double cimag(double complex);
float cimagf(float complex);
long double cimagl(long double complex);
double complex clog(double complex);
float complex clogf(float complex);
long double complex clogl(long double complex);
double complex conj(double complex);
float complex conjf(float complex);
long double complex conjl(long double complex);
double complex cpow(double complex, double complex);
float complex cpowf(float complex, float complex);
long double complex cpowl(long double complex, long double complex);
double complex cproj(double complex);
float complex cprojf(float complex);
long double complex cprojl(long double complex);
double creal(double complex);
float crealf(float complex);
long double creall(long double complex);
double complex csin(double complex);
float complex csinf(float complex);
double complex csinh(double complex);
float complex csinhf(float complex);
long double complex csinhl(long double complex);
long double complex csinl(long double complex);
double complex csqrt(double complex);
float complex csqrtf(float complex);
long double complex csqrtl(long double complex);
double complex ctan(double complex);
float complex ctanf(float complex);
double complex ctanh(double complex);
float complex ctanhf(float complex);
long double complex ctanhl(long double complex);
long double complex ctanl(long double complex);
The following sections are informative.
Values are interpreted as radians, not degrees.
The choice of I instead of i for the imaginary unit concedes to
the widespread use of the identifier i for other purposes. The
application can use a different identifier, say j, for the
imaginary unit by following the inclusion of the <complex.h>
header with:
#undef I
#define j _Imaginary_I
An I suffix to designate imaginary constants is not required, as
multiplication by I provides a sufficiently convenient and more
generally useful notation for imaginary terms. The corresponding
real type for the imaginary unit is float, so that use of I for
algorithmic or notational convenience will not result in widening
types.
On systems with imaginary types, the application has the ability
to control whether use of the macro I introduces an imaginary
type, by explicitly defining I to be _Imaginary_I or _Complex_I.
Disallowing imaginary types is useful for some applications
intended to run on implementations without support for such types.
The macro _Imaginary_I provides a test for whether imaginary types
are supported.
The cis() function (cos(x) + I*sin(x)) was considered but rejected
because its implementation is easy and straightforward, even
though some implementations could compute sine and cosine more
efficiently in tandem.
The following function names and the same names suffixed with f or
l are reserved for future use, and may be added to the
declarations in the <complex.h> header.
cerf() cexpm1() clog2()
cerfc() clog10() clgamma()
cexp2() clog1p() ctgamma()
The System Interfaces volume of POSIX.1‐2017, cabs(3p), cacos(3p),
cacosh(3p), carg(3p), casin(3p), casinh(3p), catan(3p),
catanh(3p), ccos(3p), ccosh(3p), cexp(3p), cimag(3p), clog(3p),
conj(3p), cpow(3p), cproj(3p), creal(3p), csin(3p), csinh(3p),
csqrt(3p), ctan(3p), ctanh(3p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 complex.h(0P)
Pages that refer to this page: float.h(0p), tgmath.h(0p), cabs(3p), cacos(3p), cacosh(3p), carg(3p), casin(3p), casinh(3p), catan(3p), catanh(3p), ccos(3p), ccosh(3p), cexp(3p), cimag(3p), clog(3p), conj(3p), cpow(3p), cproj(3p), creal(3p), csin(3p), csinh(3p), csqrt(3p), ctan(3p), ctanh(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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